University and Warnell faculty and researchers are helping state and federal officials in assessing and managing the impact on a principal state waterway of a potentiallydamaging invasive species – the Asian swamp eel.

In 1994, these eels were discovered in ponds at the Chattahoochee Nature Center (CNC), along the Chattahoochee River in Roswell, GA. How the eels came to the ponds is uncertain, but likely is the result of aquarium or foodfish releases.

The Asian swamp eel, although a fish, behaves more like an amphibian. It breathes air, crawls on land, and feeds like an amphibian. The presence of this exotic species in the United States is a cause of concern because it might displace native aquatic species.

Due to the CNC’s proximity to the river, the threat of eels escaping into the outlying marshes is high. The ability of the eels to reproduce in the river near this location is uncertain. However, there are areas downriver, in south Georgia and Florida, where the water is warmer and reproductive conditions ideal. The eels could travel as far as the Gulf of Mexico if a population establishes in the marshes and river outside the CNC.

In 2003, the Department of Natural Resources, the U.S. Fish and Wildlife Service, and the National Park Service collaborated with the CNC to develop a control/eradication program for the eels.

UGA researchers, including Museum of Natural History director Dr. Bud Freeman, Warnell professors Drs. Jay Shelton and Aaron Fisk, and post-doctoral researcher Dr. Tom Reinert (Warnell 2004), were recruited to conduct research at the CNC with three primary objectives: determine the impact the eels have on native species; determine the extent of the eels’ presence in the river; and finally, recommend the best way to eradicate the eels if possible, or at least control their population.

The eels’ diet was found to consist primarily of invertebrates such as insect larvae, but the eels will eat fish and other eels occasionally. However, because of the eels close similarity to amphibians, there is a higher risk of the eels outcompeting native species such as amphiumas and sirens rather than depredating fish populations.

Unfortunately, swamp eels have been found in the outlying marshes between the ponds and the river. “As for control and containment options, the eels are established in the ponds and would be nearly impossible to eradicate,” says Dr. Reinert. “Eels appear resistant to chemical control and readily burrow to avoid drought conditions—or drained pond conditions.”

“We can’t eradicate the eels—we must contain them,” says Dr. Shelton. “First we must modify the ponds so they’re not suitable for eels. We must have very little shallow water, because the eels can escape through vegetation in these shallow areas and eat invertebrates found there as well. Second, we must modify how the water flows out of the pond to the marshes. It must flow out through the deep areas in the bottom of the pond where the eels can’t breathe and won’t be found.”

UGA has recommended to the DNR, USFWS, and NPS how to best modify the ponds to accommodate these conditions, using a siphon system to drain the pond. Although the CNC is on private land, it is working with these groups to maintain the ponds for education programs and control the eels as effectively as possible.

Kate Spear is a recent Warnell graduate with a BSFR in Wildlife and a BA in French. She has contributed articles in three previous issues of the Log. Kate can be contacted at kspear@uga.edu.